Manufacture of artificial materials



v Patented May 23, 1939 I PATENT OFFICE MANUFACTURE OF ARTIFICIAL MATERIALS Henry Dreyfus, London, England No Drawing.

Application September 18, 1936,

Serial No. 101,428. In Great Britain September 23, 1935 4 Claims.

This invention relates to improvements in the manufacture of yarns and other materials, and

is more particularly concerned with processes for the production of yarns and other materials having a basis of cellulose acetate and other organic esters of cellulose, and with the new yarns and other materials produced thereby.

I have found that the resistance to heat of formed yarns, foils, films and other materials having a basis of an organic ester of cellulose, i. e., materials formed by shaping and setting compositions containing the organic ester of cellulose, may be increased by esterifying the materials, e. g., with diluted acetic anhydride, in the presence of small proportions of perchloric acid as catalyst. The esterifying agents employed are anhydrides of lower fatty acids, i. e., acids containing not more than six carbon atoms. Suitable anhydrides are propionic, butyric and especially acetic anhydrides. By this means the safe ironing point of yarns and similar materials may be increased so that they may be ironed I without damage at higher temperatures than are customary in ironing ordinary cellulose acetate artificial silk. In addition, the treatment reduces the moisture regain of the materials and they acquire a greater resistance to water, and have a substantially greater resistance to the delus-' tring action of hot or boiling aqueous liquids or moist steam. In addition, the ailinity of the yarnsv and other materials for. dyestufis in general is altered. Thus their afllnity for the dispersed insoluble dyestufis now commonly appliedto cellulose acetate is materially reduced and a longer time is required to reach any particular depth of colour, and indeed it may not be possible to reach such depth at all. By association, for example, of cellulose acetate yarns or other materials so treated with yarns or other materials of cellulose acetate untreatedby the process, differential dyeing effects are therefore obtainable, whilst at the same time the dye has an aflinity for the whole of the fabric or other material in which the two types of yarn are associated. Thus, for instance, light and dark blue shades can be produced by the immersion in a dyebath containing an SRA blue dyestufl of a fabric cone taining ordinary cellulose acetate yarn together with the same yarn which has been subjected to the process of the invention.

An important feature of the new process'is that it has the effect of changing the solubility characteristics of the yarns, films and similar materials. Thus for instance by treating a cellulose 55 acetate yarn with acetic anhydride according to the present invention, ayarn may be produced which is insoluble, or much less soluble in acetone. acteristics occur in the treatment of other yarns used as starting materials in the process of the invention. It is thus possible according to the invention to produce yarns or other materials which it is diiflcult or even impossible to manufacture by a simple spinning process.

According to the present invention, therefore, materials having improved properties are obtained by acetylating or otherwise esterifying formed filaments, yarns, foils, films and similar materials having a basis of organic esters of cellulose with liquid media comprising anhydrides of lower fatty acids dissolved in diluents withthe aid of perchloric acid as catalyst.

It is to be understood that the term yarn employed in the present specification, unless otherwise stated, includes yarns in any suitable form, for example in the form of hanks, or on perforated bobbins, or in the form of woven or warpknitted or other knitted fabrics or similar materials. Bobbins of yarn to be esterified preferably have an open wind.

Similarly, changes in the solubility char- The invention will hereinafter be described with reference to the acetylation of yarns in hank or similar form, but it is to be understood that it is also applicable to the acetylation of yarns in other forms, e. g., as fabrics and of films, foils and similar materials, and to esteriflcation of yarns, films and similar materials with anhydrides of other lower fatty acids.

The diluent employed, which is a non-solvent for the yarn under treatment, is preferably inert thereto, though it may have a swelling action on the yarn. Good results may be obtained with hydrocarbon diluents, for example benzene, xylene or other homologues of benzene, tetraand decahydronaphthalenes, and kerosene or other high boiling petroleum hydrocarbons and also ethers, e. g., normal and iso butyl and amyl ethers, car bon tetrachloride and other non-solvent chlorinated hydrocarbons.- I

When inert diluent s are employed they may contain small proportions of swelling agents for the cellulose ester, e. g., acetone, methylene ethylene ether, methylene dichloride and especially acetic acid. For example, the swelling agent may be present in aproportion of 25% or of the weight of the yarn or other material.

The degree of dilution may be adjusted so as to prevent swelling or so as to obtain some swelling of the yarn. In any case, it should be such .as to prevent any solution or incipient solution of the yarn or any fusing together of the filaments, and, further, it may be adjusted to prevent any substantial change in the lustre or quality of the material. A given amount of acetic anhydride may, for example, be dissolved in '7 or 8 or 10 up to 20 times or more its weight of xylene or other hydrocarbon. The higher dilutions are particularly conducive to avoiding change in the lustre and to avoiding shrinkage due to the swelling action-of the anhydride. In this connection it may be mentioned that the tendency of stretched yarn to shrink is considerably less than that of normal yarn. The amount of acetic anhydride no the weight of the yarn may vary very considerably according to the degree of acetylation required and the amount of the change in the properties of the material which it is desired to bring about. It is usually sufiicient to use an amount of anhydride: from half to twice the weight of the material, e. g., a proportion of 1-1 times its weight.

The reaction is preferably carried out under atmospheric pressure, though it may be effected at subatmospheric pressure or at pressures in excess of atmospheric, for example, pressures of 20 pound per square inch or more.

The materials may be impregnated with the catalyst prior to their introduction into the acetylating medium, but preferably the catalyst is present in the medium. The perchloric acid may be introduced into the acetylating medium as such, or it may be formed therein by reaction between a perchlorate, for example sodium, calcium, magnesium or zinc perchlorate and a suitable acid, for example phosphoric acid. In such case the acid may be present in an amount at leastsufficient theoretically to convert the whole of the perchlorate into perchloric acid, or it may be present in smaller proportions so that a mixture n factors, for example upon the duration of acetylation, the degree of acetylation required and the nature of the yarn or other material to be acetylated. In the case of acetylation of ordinary cellulose acetate yarn for periods of about an hour a proportion of about .1-.2% of perchloric acid on the weight of the yarn, or the use of a medium containing perchloric acid in. a concentration of about .01.005%, gives very good results. Yarns stretched or stretched and shrunk appear to be rendered by such operation more resistant to the process of acetylation according to the present invention, and it is therefore necessary in general to employ more vigorous conditions, for example a longer period of time or, what is preferred, a somewhat higher proportion of catalyst. For example, in treating stretched yarns the catalyst is preferably employed in a proportion of the order of .5 to 1% on the weight of the yarns, or in a concentration in the acetylating medium of about .05-.025%, the other conditions being as indicated above. The diluent, for example benzene, may be present in proportion of about 20 times the weight of the yarnor other material, and, as indicated above, the

presence of a small proportion of acetic acid or preferably of the order of 150 to 200% on the weight of the material.

The starting material may be a yarn produced by the ordinary spinning process, or it may be a yarn treated by any suitable after-treatment process, for example stretching, shrinking, dyeing orother processes. For example, the yarn subsequent to its manufacture may be subjected to a stretching treatment designed to increase its tenacity, e. g., with the aid of dioxane or other suitable solvent, or in the presence of steam or hot water, as described in United States specification S. Nos. 4,510 and 4,511 filed February 1, 1935. The stretching treatment may, for example, be such as to extend the yarn by 200-500% or even 1000% or more of its original length. Such yarns have an extremely high tenacity which is reflected in the final product treated according to the present invention. Such stretched yarns, or even ordinary artificial silk materials, may, if desired, be subjected to a shrinking treatment to increase their extensibility, for example 7 a shrinking treatment carried out with the aid of latent solvents (see United States Patent No. 2,058,422. As stated above, the stretching of yarns appears to render them more resistant to process. Thus hanksmay be immersed for the appropriate period in the acetylation mixture, or the mixture may be pumped or sucked through a perforated bobbin or other package of the yarn.

Example The following example illustrates the production of an improved yarn according to the process of the present invention. 20 parts by weight of ordinary dry spun cellulose acetate yarn are treated for about one hour in a mixture consisting of 400 parts by weight of benzene. about 40 parts by weight of acetic anhydride, 3 parts by weight of acetic acid and .04 part by weight of perchloric acid. After washing and d y ng a yarn is obtained which is practically insoluble in acetone, has an increased acetyl content, an improved resistance to ironing and to treatment with hot aqueous media and a decreased affinity for the ordinary cellulose acetate dyestuffs.

If, instead of normal yarn, a yarn which has been stretched, for example, to 400 to 600%ot its original length, is treated the weight of catalyst should be increased to about .1 to .15 part.

Having now described my invention, what I desire to secure by- Letters Patent is:

1. Process for the production of improved artificial materials, which comprises acetylating formed filaments, yarns, foils, films and similar materials having a basis of acetone-soluble cel lulose acetate with non-solvent liquid media comprising acetic anhydride dissolved in a suitable diluent with the aid of perchloric acid as catalyst and continuing the acetylation until products having a reduced solubility in acetone are obtained.

2. Process for the production of improved artificial materials, which comprises acetylating nor- 'mal acetone-soluble cellulose acetate filaments, .the order of 0.5 to 1% of the weight of the mateyarns and similar. materials with a non-solvent liquid medium containing acetic anhydride dissolved in a suitable diluent with the aid of perchloric acid as catalyst in a proportion of the order of 0.1 to 0.2% of the weight of the materials and continuing the acetylation until products having a reduced solubility in acetone are obtained.

3. Process for the production of improved artificial materials, which comprises acetylating stretched acetone-soluble cellulose acetate filaments; yarns and similar materials with a nonsolvent liquid medium comprising acetic anhydride dissolved in a suitable diluent with the aid of perchloric acid as catalyst in a proportion of rials and continuing the acetylation until products having a reduced solubility in acetone are obtained.

4. Process for the production of improved artificial materials, which comprises acetylating formed filaments, yarns, foils, films and similar materials having a basis of acetone-soluble cellulose acetate with a non-solvent liquid medium comprising acetic anhydride dissolved in a diluent selected from the group consisting of benzene, xylene, kerosene and carbon tetrachloride with the aid of perchloric acid as catalyst and continuing the acetylation until products having HENRY DREYFUS. 

